Inspired by natural surfaces such as lotus leaves and Nepenthes pitcher plants, researchers developed two kinds of artificial surfaces to repel liquids much more strongly than conventionally expected. Water-repellent surfaces were made by combining a simple microscale roughness to a hydrophobic material so that water beads up into near-spherical droplets, which roll on or even bouncing off the surface. This type of common superhydrophobic surface can be represented by a simple surface structure shown, for example, in FIG. 1A. To repel liquids that are more difficult to repel, such as oils and organic solvents, an overhanging microstructure (a.k.a. re-entrant topology) is additionally needed so that liquids can be suspended on top of the microstructures by upward-pointing surface tension. This type of superhydrophobic surface can be represented by a surface structure shown in FIG. 1B. However, such an approach is not effective if the liquid is a fluorinated solvent with surface tension smaller than 15 mN/m. See Grigoryev et al., Superomniphobic Magnetic Microtextures with Remote Wetting Control, J. Am. Chem. Soc. 134, 12916-12919 (2012). This is because fluorinated solvents wet all existing materials (including polytetrafluoroethylene) so strongly, e.g., Young's angle (i.e., the intrinsic contact angle of a liquid on a smooth solid surface) is smaller than 10° (i.e., θY<10°) even on polytetrafluoroethylene, that even an overhanging structure could not provide enough suspension force and consequently fails to prevent the liquid from wetting into the microstructures, making the entire surface even more wetting.
Mimicking of Nepenthes pitcher plants, on the other hand, led to a slippery liquid-infused porous surface (SLIPS), where a liquid is repelled by a thin layer of lubricating liquid infused on the porous surface. International Publication No. WO 2012/100100 illustrates one type of SLIPS structure. Limited by the working mechanism, however, SLIPS can only repel liquids that are immiscible to the lubricating liquid and have larger surface tension than the lubricating fluid. Therefore, using one of the fluorinated solvents (e.g., 3M™ FC-70) as the lubricating liquid, SLIPS provides stable repellency to aqueous and hydrocarbon liquids. However, SLIPS fails to repel other fluorinated solvents because neither the immiscibility nor the surface tension criteria is fulfilled.